1. Field of the Invention
The present invention relates generally to motive electric power systems and, in particular, to a three-wire reversing system for a permanent magnet, brush-type, direct current (DC) motor powered by an alternating current (AC) input voltage.
2. Discussion of the Prior Art
Known motive electric power systems show that the general concept of rectifying or converting an AC voltage input to power a DC motor is well known in the prior art related to DC motor drive systems. There are several examples showing this general concept in the prior art.
U.S. Pat. No. 3,670,189 to Monroe discloses a self-starting permanent magnet-type motor consisting of a fore and an aft stator assembly which will operate on batteries or alternate half cycle current.
U.S. Pat. No. 3,697,841 to Nystuen was issued to Whirlpool Corp. and discloses an induction motor with a squirrel cage rotor and an additional stator winding which, when energized in proper sequence with the original stator winding, causes rapid reversal of the motor.
U.S. Pat. No. 4,282,464 to Uzuka discloses a reversible drive circuit for a brushless DC motor including a rotor, a plurality of magnets, and a stator with at least two coils. The reversible drive circuit regulates an alternating signal through the coils. First and second switching transistors are included for energizing the coils with the alternating signal. However, this brushless DC motor is not usable in the present invention.
U.S. Pat. No. 4,731,570 to Lee discloses an electrical drive circuit for a variable-speed switched reluctance motor with a bifilar winding which may be used as a replacement for conventional induction motor drives to provide good combinations of high output power and system efficiency at considerably lower costs.
U.S. Pat. No. 4,823,037 to Abukawa et al. discloses a DC electric motor comprising: a reversibly rotatable rotor with an armature core; an armature winding and a commutator; a stator having a yoke and a plurality of field poles on an inner circumference of the yoke with each having a permanent magnet and an auxiliary pole; and a plurality of brushes arranged to be slidably electrically conductively in contact with the commutator.
U.S. Pat. No. 4,905,300 to Bhagwat et al. discloses a motor control and power system in which a pulsating DC voltage is developed by a rectifier 86 and is filtered by a capacitor 100 to facilitate application of a relatively smooth enhanced DC voltage to a motor 106 with the charged voltage of the capacitor applied across a series circuit including a rheostat 118, a resistor 126 and the motor 106. Nevertheless, this DC motor cannot be used in the present invention.
U.S. Pat. No. 5,130,624 to Bashark was issued to Whirlpool Corp. and discloses an electronic control for an automatic washing machine including a reversing permanent split capacitor motor.
U.S. Pat. No. 5,241,257 to Nordby et al. discloses a drive system for household appliances in which an electric motor has an AC-DC converter and inverter to supply electrical power to the motor. This AC motor is exemplary of the prior art and not the present invention.
U.S. Pat. No. 5,495,161 to Hunter discloses a speed control for a series universal AC/DC motor which is controlled by switching the phase angle of an AC signal with a triac power switch in response to a motor providing a phase-locked loop velocity control in which a speed command circuit provides a reference frequency corresponding to a selected motor speed.
U.S. Pat. No. 5,703,456 to Cox discloses a power converter and control system for a motor using an inductive load, such as a switched reluctance motor in which a return bus includes an energy storage device. A controller monitors both the inductive load and the energy stored in the storage device for dynamically controlling the current in the inductive load and the voltage on the storage device. Nevertheless, this switched reluctance motor is not usable in the present invention.
U.S. Pat. No. 5,818,194 to Nordby discloses a direct drop-in replacement variable speed blower motor with a neutral input and two hot AC line connections. The blower motor unit senses which input is energized by sensing either voltage or current on at least one of the inputs, selects one of the two reference signals in accordance with which input is energized, and presents the control input of the replacement variable speed motor with the selected reference signal to control the speed of the motor. However, this speed control system cannot be used with the present invention.
U.S. Pat. No. 6,051,952 to Moreira et al. was issued to the Whirlpool Corp. and discloses an electric motor speed and direction controller including a motor control for a single phase induction motor (SPIM) driven by two windings, i.e. a line winding connected to an AC line and a control winding driven by the controller. The SPIM torque, i.e. speed and direction, is controlled by the voltage output for the controller for all speed below the synchronous speed set by the AC line frequency.
U.S. Patent Application Publication No. 2003/0071592 of Lin discloses a controlling device used for an AC and DC driven motor including a converting unit, a voltage stabilizing unit, a phase detecting/controlling unit and a high voltage driving unit.
There is an additional unpatented prior art device about which the inventors are aware: This relevant prior art device is illustrated in FIG. 1. There is a permanent split capacitor PSC electrically connected to a reversible, alternating current (AC) motor. An input voltage source supplies an alternating current of 50 to 60 Hertz (Hz) to a common (COM) lead and to either a lead for clockwise (CW) motor rotation or a lead for counterclockwise (CCW) motor rotation.
This unpatented prior art three-wire system for reversing the direction of rotation of the AC motor is relatively heavy and requires a large package. Also, the prior art AC motor is an induction type with either two poles operating at about 3,450 revolutions per minutes (rpm) or four poles operating at about 1,675 rpm.
Despite the developments of the prior art, no simple and efficient three-wire reversing motive electric power system has been developed to drive a reversible, permanent magnet, brush-type DC motor using an AC power supply. This type of DC motor may be used to replace the prior art reversible AC-type motor, such as that shown in FIG. 1, and commonly found in household appliances or the like.